Preparation of isohumulone containing hop extract

ABSTRACT

An improvement in the method of preparing an isohumulone containing hop extract in which a solution of an extract of hops in a water immiscible solvent which dissolves alkali metal humulate salts less readily than does a dilute aqueous alkali metal carbonate, is contacted with such a carbonate to transfer the humulate salts into the aqueous phase and leave the lupulones in the organic phase. The improvement comprises separating the humulate salts from the aqueous phase by (i) precipitating the salts or (ii) extracting them from the aqueous phase with a water-immiscible polar solvent. The humulate salts are then isomerized by heating. The invention also includes a method for flavoring beer by adding a novel aqueous solution of potassium isohumulates which is substantially free from lupulones and fixed and essential oils of hops, to fermented beer.

United States Patent [72] Inventor William Mitchell Hatfield, England[21] Appl. No. 743,586 [22] Filed July 10, 1968 Continuation-impart ofSer. No. 594,980,

Nov. 17, 1966, abandoned. [45] Patented Sept. 21, 1971 [73] AssigneeBush Boake Allen Limited London, England [32] Priorities Nov. 17, 1965,Aug. 8, 1967 [33] Great Britain [31 48866/65 and 36469/67;

H Nov. 11, 1966, Republic of South Africa,

No. 66/6829 Nov. 13, 1967, Canada, 004,813

[ 54] PREPARATION OF lSOl-lUMULONE CONTAINING HOP EXTRACT ll Claims, NoDrawings [52] U.S. Cl 99/50.5 [51] lnt.Cl Cl2c 9/02 [50] Field of Search99/50, 50.5

[56] References Cited UNITED STATES PATENTS 3,298,835 l/l967 Hildebrandet a1. 99/505 3,364,265 1/l968 Klingcl et a] 99/505 3,451,82l 6/1969Todd et al 99/505 FOREIGN PATENTS 619,563 5/1961 Canada 99/505 1,058,9762/1967 Great Britain 99/505 Primary Examiner-Joseph M. GolianAttorney-Herbert H. Goodman ABSTRACT: An improvement in the method ofpreparing an isohumulone containing hop extract in which a solution ofan extract of hops in a water immiscible solvent which dissolves alkalimetal humulate salts less readily than does a dilute aqueous alkalimetal carbonate, is contacted with such a carbonate to transfer thehumulate salts into the aqueous phase and leave the lupulones in theorganic phase. The improvement comprises separating the humulate saltsfrom the aqueous phase by (i) precipitating the salts or (ii) extractingthem from the aqueous phase with a water-immiscible polar solvent. Thehumulate salts are then isomerized by heating. The invention alsoincludes a method for flavoring beer by adding a novel aqueous solutionof potassium isohumulates which is substantially free from lupulones andfixed and essential oils of hops, to fermented beer.

PREPARATION OF ISOHUMULONE CONTAINING HOP EXTRACT The presentapplication is a continuation-in-part application of applicantscopending U.S. Pat. application Ser. No. 594,980filed Nov. 17, 1966 andnow abandoned.

The present invention relates to the manufacture of hop extracts and tothe flavoring of beer therewith.

Hops contain resins, oils, waxes, water soluble material such astannins, proteins and pectins, and a matrix of cellulosic material. Theresins consist of the soft resins, which include the humulones andlupulones, and the hard resins." The oils consist of the volatileessential oil and the relatively involatile fixed oil.

The term humulone is used generically herein to include the a-acids suchas are present in hops, e.g. humulone, cohumulone, adhumulone andposthumulones. The water soluble salts of the aforementioned humulonesare referred to herein as humulates." Isohumulones" includes thecompounds isohumulone, isocohumulone, isoadhumulone and isoposthumuloneswhich may be prepared by isomerizing the corresponding humulones. Theterm lupu1ones" as used herein includes the weakly acidic B-acids ofhops. Fixed oil refers to the relatively involatile oil contained in thehop seeds which is not removed by the boiling water in conventionalbrewing operations. Essential oil" refers to the relatively volatileoils which contribute to the aroma of hops.

In the traditional brewing process hops are boiled with wort prior tothe fermentation step. In the course of this boiling, part of the softresins (comprising humulones) is isomerized into a water soluble formand dissolves in the wort. It has been realized that it is this watersoluble isomerized material, comprising isohumulones, which isprincipally responsible for the bitter flavor of beer. The traditionalprocess has man disadvantages; e.g. it is necessary to store a largebulk of hops which are subject to slow deterioration; it is difficult toobtain a consistent degree of bitterness; and, in particular, only asmall proportion of the humulones present in the hops appears in thewort as isohumulones after boiling, so that much of the potentialbitterness is wasted.

A number of attempts have been made to extract the essential flavoringingredients from hops using organic solvents. One disadvantage of suchextracts is that in addition to the humulones and other desirable hopingredients the organic solvent tends to remove undesirable hopingredients which can give rise to unpleasant flavors. Moreover, theextracted humulones upon addition to boiling wort are only partiallyutilized.

In order to prepare isohumulones efficiently, it has been proposed tocontact the humulones with hot alkali. The principal disadvantage ofthis technique is that when hops or hop extracts are contacted with hotalkali, certain other ingredients apart from the humulones undergodegradation giving rise to disagreeable flavours.

Various methods have been proposed for separating the humulones from theother hop extractive in order to prepare pure isohumulones, but thesemethods have generally been too costly for commercial application.Moreover, pure isohumulones do not impart the full flavor of traditionalbeer, and

' their exclusive use may result in wastage of other flavor ingredientspresent in the hops.

In our copending application Ser. No. 629,905 filed in Apr. 1967, wehave described methods by which undesirable flavoring ingredients, suchas fixed oils, can be eliminated from the hop extract by fractionatingthe extract in aqueous methanol; and methods by which the humulones maybe isomerized with hot alkali, without generating the usual offflavors,by dissolving the extract in a water immiscible solvent, partitioningwith aqueous alkali isomerizing and recovering isohumulones from theaqueous phase. However, it has been found that further losses ofisohumulones occur when isomerized extracts prepared in this way areadded to beer. This is due to the entrainment of isohumulones by waterinsoluble resinous material such as lupulones which are coextracted bythe alkali and which precipitate in the beer.

We have discovered that it is possible to prepare an extract of hopscomprising a high proportion of isohumulones substantially free oflupulones, fixed oils and unpleasant alkali degraded material, if asolution of hop extract in a water-immiscible solvent which dissolveshumulate salts less readily than does water, is contacted with aqueousalkali at a pH sufficient to transfer the a-acids into the aqueous phaseas humulate salts but not sufiicient to transfer the lupulones into theaqueous phase as lupulate salts. We have further discovered that theother desirable hop ingredients, including essential oils and lupulonesmay be conveniently used provided that they are separated from thehumulones prior to the isomerization thereof, freed from any fixed oilsand added to the wort as a kettle adjunct prior to the isohumulones.

Prior methods of preparing isomerized hop extracts have generallyrequired the boiling of a dilute alkaline solution of humulates wherebythe solution is: evaporated to form a concentrated solution which isfinally dried under reduced pressure to an anhydrous powder. We havefound that the extensive boiling required by this technique causes somedegradation of humulone into less useful substances and is moreover veryexpensive in terms of heat energy.

We have discovered that the product is improved and considerable savingsin production costs achieved if the humulones are recovered from thedilute solution by precipitation with an alkaline earth metal of bysolvent extraction. We have further discovered that soft extractscontaining 10 to 25 percent by weight of water are more convenient tohandle than anhydrous extracts (which may be unpleasant to workershandling them) and are, moreover, easier to dissolve in water beforeaddition to wort or beer.

Hitherto, it has been customary to employ sodium alkalis for separatingand/or isomerizing humulones, although it has been suggested that otheralkalis might also by employed. In practice, we have found that asomewhat superior separation of humulones may be obtained using thesodium alkalis. Surprisingly, we have now discovered that the potassiumsalts of the isohumulones are superior to the sodium salts as bitteringagents for beer and like beverages.

An object of our invention is therefore to provide a convenient andeconomical process for isolating isomerized humulones and otherdesirable hop resins in high yield from hops, and substantially freefrom hop ingredients which give rise to off flavors. A further object ofour invention is to provide improved bittering agents which are readilysoluble in wort or beer. A further object of our invention is to providemeans for the bittering of beer which provide a consistent and naturalflavor without wastage of the bitter'ingredients of the hop.

The invention may be summarized as residing in methods for thepreparation and use of isomerized bittering agents for beer comprisingthe following steps:

I. The separation of humulones from humulone-containing hop materialinto a dilute aqueous solution as alkali metal humulate: Desirably, thehumulones are separated from substantially all the oils, both fixed andessential and from any hop wax. Preferably, the humulones are alsoseparated from at least the more water insoluble of the soft resins,including at least most of the lupulones. The separation is convenientlybrought about by obtaining a solution ofa solvent extract of hops in awater immiscible, relatively nonpolar solvent and contacting it with anaqueous alkaline solution containing alkali metal ions. The preferredalkaline solutions are of salts which have a buffering action and mostparticularly carbonates. It may sometimes by desirable to include aminor proportion of water miscible organic solvent, e.g. methanol withthe alkali, but this is not essential. The best alkali metal ion at thisstage is sodium; but potassium may also be employed. If potassium isemployed it is preferred to wash the aqueous extract with awater-immiscible relatively nonpolar solvent e.g. petroleum orpreferably benzene.

2. The concentration of the dilute solution of humulate salts: This ispreferably effected by transferring the humulones from the dilutesolution into a smaller bulk of a different solvent, preferably withoutsubstantial boiling or evaporation of the dilute solution, and mostdesirably while maintaining the solutions at ambient temperature. E.g.the humulones may be precipitated as a water insoluble salt of apolyvalent cation, redissolved in a second solvent, and converted backinto an alkali metal humulate by treatment with an alkali metal salt ofan anion which precipitates the polyvalent cation. Alternatively, thedilute solution of humulate may be contacted with a polar,water-immiscible solvent which dissolves humulates more readily thanwater, into which the humulates pass. Preferably, if the humulates arenot already present as a potassium salt, they are converted into apotassium salt at this stage, e. g. by ion exchange resins; byneutralizing a solution in a water-immiscible solvent with dilute acid,neutralization and extracting the water-immiscible solution with anaqueous alkaline solution containing potassium ions; or by contacting anorganic solution of the humulate of a polyvalent metal cation with, forexample, potassium carbonate.

3. isomerization: This may be effected by various means but preferablyby boiling an aqueous solution of sodium or potassium humulate,preferably potassium humulate. The isomerized alkaline aqueous solutionmay then be washed with petrol if desired. If the isohumulone is notpresent as a potassium salt at this stage it may be converted into one,using, for example, one of the methods described under (2) above. Theisomerization may be carried out in the dilute solution prior to theconcentration by (2) above, but it is preferred to isomerize aconcentrated solution of humulates in order to reduce heating costs.

4. Preparation of a bittering extract: The isohumulate may be used asthe aqueous solution, but preferably it is evaporated to form a softalkaline extract containing l-25 percent water. Drying to a solid andpowdering is possible but very much less preferred. If desired theisohumulate may be blended with emulsifying salts, diluents and/or watersoluble salts of other hop resins, e.g. alkali metal hulupates, andoptionally, hop essential oils.

5. Addition of the bittering extract to beer: This may occur eitherbefore or after fermentation. Preferably, however, the bittering extractis added as an aqueous solution to fermented beer. Conveniently, thebeer may already have been partially flavored by boiling with hops or byaddition of a kettle adjunct comprising, for example, hop resins, suchas lupulones or hulupones, and hop essential oils.

Our invention provides a method of preparing an isohumulone containinghop extract which comprises contacting a solution ofa solvent extract ofhops in a water immiscible solvent with an aqueous alkali at a pHsufficient to transfer at least a major part of the humulones into theaqueous phase to form a dilute aqueous solution of humulates, whileleaving at least a major part of the lupulones in the nonaqueous phase,separating'the aqueous and nonaqueous phases, heating the humulates insolution to effect isomerization thereof and recovering the humulonesfrom the dilute aqueous phase, at the latest after the isomerization, byprecipitation with an alkali metal cation or by extraction with arelatively polar water immiscible solvent.

Our invention also provides a method of bittering beer which comprises:preparing a bittering additive comprising isohumulones substantiallyfree from fixed oils, essential oils and lupulones and a kettle additivecomprising lupulones and essential oils substantially free from fixedoil; converting the humulones in the bittering additive intoisohumulones; adding the kettle additive to wort and subsequently addingthe isomerized bittering additive.

According to one aspect our invention also provides a method offlavoring beer which comprises adding a potassium isohumulate salt towort or fermented beer.

Our present invention, according to a further aspect, provides a methodof preparing an improved bittering extract for beer which comprisescontacting a solution of a humulonecontaining hop material in asubstantially water-immiscible solvent which dissolves alkali metalhumulates less readily than water, with an aqueous alkali containingsodium ions at a pH sufficient to transfer the humulones into theaqueous phase as sodium humulates, separating the aqueous phase from thewater immiscible phase and subsequently converting the sodium humulatesto potassium humulates.

According to a further aspect our invention provides a method ofpreparing a bittering extract for beer which comprises contacting asolution of a hop extract in a water immiscible solvent which dissolveshumulates less readily than water with aqueous potassium carbonatewashing the aqueous solution with a water immiscible solvent thatdissolves humulates less readily than water, and isomerizing thepotassium humulates.

According to a further aspect our invention provides a method offlavoring beer which comprises preparing a bittering extract comprisingpotassium isohumulates, and a copper adjunct comprising lupulones, orderivatives thereof, adding the copper adjunct to wort and at asubsequent stage in the brewing operation adding the bittering extract.

The humulone-containing hop material, which is dissolved in the waterimmiscible solvent in order to prepare the bittering extract accordingto our invention is desirably an extract of hops containing humulones,lupulones and other resins, and oils. Such a material may convenientlybe prepared by extracting hops with an organic solvent, e.g.hydrocarbons, alcohols, ketones such as acetone, and chlorinatedhydrocarbon sol vents. We have discovered that benzene, or preferablyparaffms such as hexane are particularly suitable.

The humulone-containing hop material may alternatively comprise a partlypurified extract, e.g. an extract from which fixed oils and/or waxeshave been separated.

Preferably, the initial extraction of the hops is carried out on roastdried hops. However, vine fresh or freeze dried hops may also beemployed. Normally, the hops are ground in a high speed hammer mill andpercolated with sufficient of the extracting solvent to remove at leasta major part of the soluble components.

In order to carry out the contacting with aqueous sodium alkali, asolution of crude hop extract in the extracting solvent may be employed,providing the latter is water immiscible and dissolves alkali metalhumulate salts less readily than does water. We have found that the bestwater-immiscible solvents for use in the contacting step are nonpolarhydrocarbons, e.g. petroleum ether is especially suitable. if desired,the original extracting solvent may be evaporated off and the crudeextract dissolved in the water immiscible solvent of the contactingstep. Alternatively, where a suitable solvent such as benzene or hexaneis employed for the extraction, the initial solution of extract may beconcentrated by evaporation of part of the extracting solvent and theconcentrated solution contacted with the aqueous sodium or potassiumalkali, using for example, a countercurrent extractor.

The aqueous alkali for use in the contacting step is preferably aqueoussodium or potassium carbonate (carbonates are particularly preferredsince the bicarbonate is formed during the transfer of the humulones,and acts as a buffering agent). The alkali should be used in sufficientquantity to provide a final pH which will extract humulones as humulatesbut preferably not sufficient to extract the lupulones as lupulates. Thepreferred pH of the aqueous phase immediately prior to separation fromthe organic phase depends on the water-immiscible solvent selected. Inthe case of petroleum ether the pH may be in the range of9 to 9.5, togive sufficient removal of the humulones but not of any substantialquantity of lupulones. Where benzene is used the pH may be up to 9.8.The alkali should be sufficiently dilute to avoid salting out thehumulones by any bicarbonate formed during extraction. For example, asolution of less than 5 percent w/v carbonate and preferably less than 3percent w/v carbonate is suitable, 2.5 percent to 2 percent w/vcarbonate has been found to give especially good results. If desired,the partitioning may be carried out in two or more stages. For examplein the first stage the pH of the final mixture may be 9 to 9.2. Theaqueous phase will be separated and the organic phase contacted withportions of alkali at successively high pH. Each portion of alkali iscontacted with successive portions of fresh organic solvent solutionuntil the pH reaches the desired final level and is then removed.Alternatively, the whole contacting operation may be performed in asingle continuous countercurrent extractor.

We have found that aqueous sodium carbonate gives a better separation ofthe desirable hop resins from worthless or undesirable hop ingredientsthan does potassium carbonate, but that high quality extracts may beobtained using aqueous potassium carbonate if the aqueous phase iswashed with a nonpolar water immiscible solvent such as petroleum ether,after separation from the nonaqueous phase.

A difficulty we have encountered when humulones are separated by theabove technique, where the sodium or potassium humulates must berecovered from a dilute aqueous system, is the considerable cost ofevaporating the large volume of water to recover the extract. Moreover,the humulones are liable to deterioration upon prolonged heating. Wehave discovered that the humulones may be recovered from theaqueoussolution by adding thereto the water soluble salt of metal whichforms a water insoluble humulate salt.

The salt used to precipitate the humulones may be any water soluble saltof a cation whose humulate salts are insoluble in the aqueous solutionand whose carbonate is preferably insoluble in concentrated aqueousmethanol, for example an alkaline earth metal, preferably calcium ormagnesium. The anion is not important. For example any water solublechloride, bromide, iodide, sulfate, nitrate, acetate or similar salt ofa metal such as calcium or magnesium may be employed. Other metals suchas zinc, copper, strontium or nickel are operative, but are normallyless preferred on account of their toxicity, which necessitatesstringent precautions. Whether any particular salt is suitable canreadily be determined by trial and error.

The precipitated humulate salt may be filtered, dissolved in a suitableorganic solvent, e.g. methanol, and is preferably then converted toalkali metal humulate by adding a concentrated aqueous solution of analkali metal carbonate, preferably potassium carbonate, whereupon aninsoluble metal carbonate precipitates. The former precipitate,comprising insoluble humulate salts, is normally contacted while stillwet with methanol (e.g. 97 tolOO percent methanol) sufficient to give atleast 90 percent w/v methanol in the solution. The alkali metalcarbonate is added in the form of a concentrated aqueous solution. Theresult is that after removal of the precipitated carbonate (e.g. byfiltration) and the methanol (e.g. by evaporation), there is left aconcentrated aqueous solution of the potassium humulates. Where thehumulate has not already been isomerized, this solution, after anynecessary adjustment of pH and concentration, may be boiled to isomerizethe humulones. It is also possible to isomerize the humulones prior tothe precipitation of the insoluble salt, in which case an isohumulatesalt is precipitated.

As an alternative to the above described method of converting aninsoluble metal humulate or isohumulate in an alkali metal humulate orisohumulate, it is also possible to employ a suitable cation exchangematerial (e.g. a cation exchange material of the type sold commerciallyas Zeo Karb 2), in order to remove the unwanted metal ion from themethanolic solution. The resulting solution may then be neutralized topH 9 to 10.2, preferably with KOH. The methanol is recovered and theneutralized extract is boiled.

We have discovered that although either sodium or potassium carbonatemay be used in the partitioning step, the isomerization step is mosteffectively performed on the potassium humulate. We therefore prefer tocontact a water-immiscible solution of unixomerized hop material withaqueous sodium or potassium carbonate, separate the aqueous phase,recover the humulate salt from the aqueous phase, convert the humulateif necessary into a potassium humulate and subsequently isomerize thepotassium humulate by boiling.

In order to avoid the filtration steps necessary when insoluble humulatesalts are precipitated, we have devise an alternative method forseparating the humulates or isohumulates from the aqueous solution.According to this alternative we prefer to contact the aqueous solutionof alkali metal humulates or isohumulates, after separation from thewater-immiscible solvent, with a volatile, polar, water-immisciblesolvent, which is sufficiently polar to extract alkali metal humulatesfrom the aqueous solution. The alkali metal humulates may be salted outby addition of a water soluble salt of the alkali metal e.g. wheresodium carbonate has been used for the initial partition, NaCl may beemployed to salt out the sodium humulates. The preferredwater-immiscible polar solvents include relatively low boiling esterssuch as ethyl or isopropyl acetate, ketones such as methyl isobutylketone, and water-immiscible alcohols such as n-butanol.

If, desired, the sodium humulates or isohumulates may be converted topotassium salts in solution. isomerized example the solution in thepolar solvent may be shaken with excess of aqueous mineral acid andwashed with water to remove the acid Temperatures any residual alkalimetal salt used in the salting out operation. The humulones so preparedmay be con verted to potassium humulates e.g. by addition of aqueous KOHsufficient to bring the pH to about 9. The potassium humulate may beisomerized if necessary, by first boiling off the water immisciblesolvent, adjusting the pH to about 10, and then boiling the remainingaqueous solution.

Humulones, separated from lupulones and essential oils in accordancewith this specification may be isomerized by aqueous alkali. Preferablythe pH is in the range 10.0 to ll (e.g. 10.2). Temperatures above C. arepreferred e.g. boiling point.

The isohumulate-containing extract is preferably added to beer as abittering extract after fermentation.

The bittering extract typically contains a proportion of soft resins inaddition to the isohumulate, but is preferably substantially free of thewater insoluble or sparingly soluble resins such as the B-acids whichtend to lower the solubility of the extract in beer and so inhibit thefull utilization of the isohumulones. Desirably, the bittering extractis separated as much as is practicable from the hard resins and coloringmatter.

We have discovered that when humulones have been separated from awater-immiscible solution by contacting with aqueous alkali andsubsequently isomerised by heating in alkali, characteristic flavors,due to traces of unidentified material, sometimes arise during theisomerization. These flavours may be unacceptable to some palates and wehave discovered that they may be reduced by contacting the aqueousisomerized extract with a water-immiscible, relatively non polarsolvent, such as benzene or, preferably, petroleum ether.

Preferably the solution of isohumulates is evaporated to leave a softextract containing, for example 10-25 percent water. This extract mayconveniently be dissolved in water prior to addition to wort or beer.

Where a copper adjunct is employed, it preferably comprises lupulones,and/or hulupones. Preferably the copper adjunct also comprises at leastpart of the less steam volatile portion of the essential oils. Thecopper adjunct normally contains other soft resins together with somehard resins, but is desirably free of fixed oil, hop waxes and methanolinsoluble materials.

Hop ingredients remaining in the water-immiscible solvent used in theinitial contacting step or steps, may be recovered from thewater-immiscible solvent after separation from the aqueous phase andfreed from any fixed oil and hop waxes by redissolving in aqueousmethanol as described in our application No. 629,905. The purifiedmaterials may comprise lupulones and essential oils, together with softand hard resins, and

may be added to the wort. The wort should then be boiled, therebyremoving the more volatile fractions of the essential oils leaving onlythe traces of the less volatile fractions normally present in beer.Alternatively, the mixture comprising lupulones and essential oils maybe refined, e.g. by steamdistillation prior to addition to the wort orbeer. The lupulonecontaining adjunct should be added in any case priorto the isohumulone-containing adjunct.

If desired, the copper adjunct may comprise, or be used in conjunctionwith, other hop ingredients such as the water soluble materials whichare normally present in hops e.g. tannins and soluble proteins. Theadjuncts according to our invention may be used in conjunction withordinary hops.

Any fixed oil may, if desired, be removed from the initial extract priorto the step of dissolving in the water-immiscible solvent used in theinitial contacting with aqueous alkali. For example, the initial extractmay be dissolved in 80 to 95 percent aqueous methanol as described inthe aforesaid application No. 629,905. If desired, the lupulones fromthe hops may be converted to hulupones by appropriate chemicaltreatment, e.g. alkaline oxidation.

The invention will now be described in more detail in the followingexamples:

Example 1 Hop extract (146 lb.) obtained by extracting dried hops withbenzene and containing 26.9 percent humulones was dissolved in petroleumether (8.1. 75-95; 74 gallons) and the insoluble matter reserved. Theresultant solution was agitated vigorously with 2 percent aqueous sodiumcarbonate solution 180 gallons total) added in gallon quantities afteran initial quantity of 150 gallons, until the pH of the aqueous phasereached a value of 9.1, the aqueous layer was run off and washed withclean petroleum ether (B.P. 75-95; 50 gallons). The washed aqueoussolution was reserved and the relatively clean petrol layer was usedtogether with a further quantity (20 gallons) of clean petrol todissolve a further quantity (141 lb.) of hop extract. The initialpetroleum solution, from which the greatest part of humulones had beenextracted, was further extracted with 2 percent w/v aqueous carbonatesolution (150 gallons) to a resultant pH of 10.2 this solution was usedas the first extracting solution for the second quantity of hop extractalready dissolved in petroleum ether, the volume (152 gallons) beingsufficient to achieve a pH value of 9.1 after agitation. The aqueoussolution was run off and washed with clean petroleum ether (B.P. 75-95C.; 50 gallons) then reserved for a further treatment.

The two reserved aqueous solutions (pH 9.1 were treated with 25 percentaqueous solution of calcium chloride (18 gallons) and the resultantprecipitate of calcium salts collected on a vacuum filter. Withoutdrying, the precipitate was dissolved in absolute methanol 180 gallons)and the resultant solution treated with 50 percent w/v aqueous potassiumcarbonate 1 llgallons) to raise pH to 12.0. The precipitated calciumcarbonate was removed by filtration and the pH of the filtrate reducedto a value of 9.0 by the addition of 25 percent w/v aqueous citric acidsolution (6 pints). The methanol was then recovered by distillationunder vacuum. To the residue was added sufficient distilled water togive a total volume of 55 gallons and sufficient 50 percent w/v aqueouspotassium carbonate (10 pints) added to give a pH value of 10.1. Thesolution was then boiled at atmospheric pressure for 50 minutes toachieve isomerization.

The solution was cooled and then extracted with three portions of 10gallons each of petroleum ether, boiling being 75-95 C. The aqueoussolution was then evaporated under reduced pressure.

The residual petroleum ether solution from the first contacting stagewas distilled to recover the solvent and the residue together with thereserved petrol insoluble residue was purified by treatment with 90percent w/v methanol, to reject unwanted hop seed oil and othermaterial. By recovering the methanol a copper additive lb.) rich inlupulones and essential oil of hops was obtained.

It was found that isohumulate salts were obtained in a significantlyhigher yield than in a comparable process using sodium carbonate inplace of potassium carbonate, and that the product had satisfactorystability and was superior to sodium isohumulate as a bittering agent.

Example 2 1000 ml. of a solution containing 5 percent sodiumisohumulates in distilled water, was extracted with 3x200 ml. portionsof n-butanol and the isohumulate free aqueous solution was discarded.The n-butanol extractions were combined and thoroughly washed withsufficient N HCL solution (150-200 ml.) to give a pH of 1.0 in the acidlayer.

After rejecting the acid liquor, the n-butanol phase was reequilibratedwith 5 percent w/v KOH solution (approximately 300 to 350 ml.) until apH of 10.5 was reached in the alkaline phase.

The alkaline solution was separated and back extracted with a further100 ml. of fresh n butanol to recover entrained potassium isohumulatesinto the n-butanol layer.

The n-butanol solutions were mixed together and the solvent recovered byvacuum distillation; sufficient water was added towards the end of therecovery process to azeotrope with the remaining trades of n-butanol andgive a final isomerised hop extract containing about 20 percent waterand 50 percent potassium isohumulates. The product was superior to thesodium isohumulate as a bittering agent for beer.

Example 3 Ground dried hops were extracted with light petroleum ether(B.P. 75 to C.) at a temperature of 30 C. Most of the solvent wasremoved from the extract by distillation and a concentrate containingapproximately 20 percent weight by volume total solids in the petroleumether was carried forward to the next stage. This solution was agitatedvigorously with a dilute solution (2.5 percent w/v) of potassiumcarbonate in water, the addition of this latter solution being continuedgradually until the pH of the aqueous phase reached 9.0 to 9.2. Themixture was allowed to settle and the aqueous layer run off andreserved. The petroleum ether solution was then agitated with furtherpotassium carbonate solution, progressively added until the pH reached avalue of 10.0 to 10.2, the mixture was allowed to settle, and the lowerlayer was then runoff. This secondary solution contained a smallquantity of the desired humulones, not removed by the first treatment,but in addition it contained some lupulones. It was used as the firstpart of the solution required to extract the humulones from a furtherquantity of petroleum ether solution of hop extract, when the lupuloneswere removed from it by the petroleum ether; further potassium carbonatesolution was then gradually added to raise the pH value to 9.0 to 9.1.The initial aqueous solution pH 9.0 to 9.2) from the first andsubsequent batches of hop extract was washed with clean petroleum ether,to remove any remaining unwanted material, and then treated with a 50percent w/v aqueous solution of calcium chloride in distinct excess, toprecipitate the calcium salts of the desired hop acids. The calciumsalts of the humulones were collected by vacuum filtration or by meansof a centrifuge, and, while still moist, were dissolved in methylalcohol. The insoluble solid, consisting of calcium carbonate andbicarbonate was not removed at this stage. Potassium carbonate (50percent w/v in water) was added to the methanolic solution until a pHvalue of 12.0 to 2.2 was obtained; this caused the completeprecipitation of the calcium ions in the form of calcium carbonateand/or bicarbonate, the humulones being converted to their solublepotassium salts. The insoluble calcium carbonate and bicarbonate wereremoved by filtration, the filtrate was adjusted to pH 9.8 to 10.2 withcitric acid and the methanol removed from it by distillation underpartial vacuum. The residual aqueous solution of the potassium salts ofthe humulones was diluted with more water to produce a Ex mpl 5tractable solution containing 30 percent w/v total solids, boiled forapproximately 45 minutes to effect isomerization, then concentrated byvacuum distillation to a soft extract, containing to 20 percent ofwater. The soft extract could be dried under vacuum to a dry productwhich could be powdered. Products obtained in accordance with the aboveprocedure contained from 40 to 60 percent of isohumulones, and weresuitable for addition to unhopped or lightly hopped beer afterfermentation.

Hop extract (40 lb.) obtained by extracting cast hops with benzene andcontaining 32.4 percent humulones (by conductivity), was dissolved in 20gallons of benzene. This benzene solution was countercurrent extractedwith 2 percent aqueous sodium carbonate solution at a temperature of 40C in a Rotating Disc Contactor. The relative rate of flow of the aqueouscarbonate to benzene solutions was 20 gallons/hour to 10 gallons/hour atsteady state conditions. The aqueous carbonate solution from thecontactor (55 gallons) at a pH 9.7

The petroleum oth r lu n r whiCh the humulones was collected andfiltered to remove entrained material. The had been extracted, wassubjected to distillation to recover the clear fil was he d o 40 C, andtreated with 20 lb, of solvent. The resultant extract which containedlupulones and ((j cl 6H 0) di l d i 5 ll f water. Th precipitated otherhop resins, and hop essential oil, in addition to undesiral i salts wereb i d b fil i ff th aqueous luhis P seed oil and other constituents, wasPurified with tion in a basket centrifuge. The calcium humulates weredis- 85 percent aqueous methyl alcohol as described in our specifiolvedin gallons of warm (40 methanol and per. cation No. 629,905 and wasfound suitable for use as a kettle cent aqueous potassium -b t (2,5allon was additive" in th product n f beer na g desirable 6011- added toraise the pH to 12.0. The .resulting precipitate was stituents,including the essential oil of hop and lupulones to be removed b fil atid the lear filtrate wa ba k adju ted utilized o h best advantage to pH9.0 with saturated citric acid solution (70 ml.) and the t methanolrecovered under vacuum at a temperature of 40 C.

xamp e recovery was dissolved in 5 gallons of distilled water, the pHHop extract (150 lb.) obtained by extracting dried hops was adjusted to10.0 with 25 percent w/v aqueous potassium Wi h n n n ta ni g Percenthumulones y Concarbonate solution and the humulones were isomerized toy); was dissolved in Petroleum ether isohumulones by boiling atatmospheric pressure for 1.5 50 g The insflluble matter was discarded nh hours. On completion, the solution was rapidly evaporated to solutiondivided into three equal parts by volume (22 gallons 30 a soft extractunder vacuum to yield 20 lb. of finished product. each) Each Portion waseXh'acted with 2 Percent aq The product-tested 50 percent isohumulonesby C.C.D. analysodium carbonate solution at 40 C. in counter currentfashion i gi ing a recovery of 77.2 ercent from the humulones conto pH9.0-9.1 as indicated in the following table: tained in the original hopextract.

Petrol solution 1 Petrol solution 2 Petrol solution 3 1 t xtractio Add40 allons alkali Add a ueous base from 2d extraction Add aqueous phasefrom 2nd extraction 8 e n (pH 5515). or sol ution l iilus 5 gallonsalkali (pH of solution 2 plus 5 gallons alkali (pH Organic phase.Organic phase. OrEanici DhaSe. 2d extraction Add 40 gahons alkali Addaqueous phas irom 3d extraction Add aqueous phase from 3d, extraction(pH 10?. or solution 1 (pH $0.15). or solution 2 (pH 10.2).

Organ 0 phase. organic phase. 3d extraction Add 40 gahons alkali Add 40gallons alkah (pH 10.4).

The three aqueous solutions at pH 9.15 and 9.05 were The extractedbenzene solution, now free of humulones, bulked and washed withpetroleum ether (B.P. 74 95 C.; was distilled to recover the benzene.The residue (25 lb.) was gallons) 50 freed from hop seed oil and otherundesirable constituents by The resultant washsd aqueous solution (totalVolume dissolution in 90 percent w/v methanol, rejecting the insoluble gwas heated with a saturated aqueous solution of material and recoveringthe methanol, to give a kettle additive um chloride 15 gallons) andextracted with three portions of (12 lb.) rich in lupulones and hopessential oil. ethyl acetate (each of 15 gallons). The resultant ethylacetate w claim; solutions were combined and treated with 10 percent w/v1 The method f preparing an isohumulone comaining hop aqueoushydrochloric 391d (10 gallons)- After thorough aglta' extract whichcomprises contacting a solution of an extract of tion the mixture wasallowed to Separate and the lower q hops, the solvent of said solutionbeing a water-immiscible sol- Ous Phase whoffahd discarded- The ethylacetate solutiohwas vent which dissolves alkali metal humulate saltsless readily treated with 10 percent w/v aqueous potassium hydroxidethan does water, with a sufficient amount of a dilute aqueous Thepotassium humulone concentrate after methanol (q y gradual addition withstirring the P" of alkali metal carbonate to form a mixture of saidwater-immisaqueous Phase reached This Towel aqueous y r was ciblesolvent solution and said dilute aqueous alkali metal carhoff andreserved- The Solvent was "moved from the ethyl bonate having a pHsufficient to transfer the humulones into acetate solution bydistillation and the reserved aqueous layer h aqueous ha e a humulatesalts but not sufficiently high added to the l'esidue- The P of theaqueous solution was to transfer the lupulones into the aqueous phase aslupulate j l a Value Of lilo by the fiddilioh 0f 2 percent salts,forming a water-immiscible phase containing the lupuaqueous Potassiumcarbonate (qand the mixture boiled at late salts and a dilute aqueousphase containing the humulate atmospheric pressure for 90 minutes, toachieve isomeriza- Salts separating id dil aqueous phase f id w -iliOIlmiscible phase, adding to said dilute aqueous phase a water Theisomefiled solution was evaporated soluble salt of a cation whosehumulate is water insoluble to vacuum, 10 g the required P -l, as a 50ftX- form the water insoluble humulate and precipitating said tractcontaining 48.8 percent isohumulones (by countercurwater insolublehumulate salt, separating the precipitated hurent n y i and and 20residual rmulate salt from the dilute aqueous phase, dissolving saidTherefore, the conversion recovery of isohumulones from precipitatedhumulate salt in a solvent therefor, adding to the the starting materialwas 73.6.percent of theory. 7 solution of the humulate in the saidsolvent therefor a precipitant for the said cation thereby precipitatingthe said cation, separating the precipitated cation from the solution,forming an alkali metal salt of said humulate, and isomerizing thehumulate by heating said alkali metal salt thereof.

2. The method of claim 1 wherein the precipitated humulate salt isdissolved in an aqueous alkali metal solution to produce a solutionwhich contains a higher concentration of said humulate salt than did thedilute aqueous solution from which the humulate salt was precipitated.

3. The method of claim 2 wherein the said cation is selected fromcalcium and magnesium.

4. The method of claim 3 wherein the solvent for the water insolublehumulate is aqueous methanol.

5. The method of claim 4 wherein the precipitant for cation is selectedfrom carbon dioxide and alkali metal carbonates.

6. The method of preparing an isohumulone-containing hop extract whichcomprises contacting a solution of an extract of hops, the solvent ofsaid solution being a water-immiscible solvent which dissolves alkalimetal humulate salts less readily than does water, with a sufficientamount of a dilute aqueous alkali metal carbonate to form a mixture ofsaid water-immiscible solvent solution and said dilute aqueous alkalimetal carbonate having a pH sufficient to transfer the humulones intothe aqueous phase as humulate salts but not sufficiently high totransfer the lupulones into the aqueous phase as lupulate salts, forminga water-immiscible phase containing the lupulate salts and a diluteaqueous phase containing the humulate salts, separating said diluteaqueous phase from said water-immiscible solvent, said water-immisciblesolvent being sufficiently polar to extract the humulate salts from saiddilute aqueous phase, recovering said humulate salts from saidwater-immiscible solvent, forming a concentrated aqueous solution ofsaid humulate salts and isomerizing said humulate salts by heating saidconcentrated aqueous solution.

7. The method of claim 6 wherein the water immiscible polar solvent isselected from low boiling esters, ketones and water-immiscible alcohols.

8. Method according to claim 6 wherein a water soluble salt having thesame alkali metal cation as the humulate is added to the aqueous phaseprior to the separation thereof from the water immiscible phase.

9. Method according to claim 8 wherein the water immiscible polarsolvent is contacted with excess aqueous mineral acid after separationfrom the aqueous alkali phase.

10. Method according to claim 9 wherein the acidified solution iscontacted with potassium hydroxide.

11. Method according to claim 10 wherein potassium humulates arerecovered from the acidified solution by evaporation of the waterimmiscible polar solvent and isomerized by contacting with a hot aqueouspotassium alkali.

2. The method of claim 1 wherein the precipitated humulate salt isdissolved in an aqueous alkali metal solution to produce a solutionwhich contains a higher concentration of said humulate salt than did thedilute aqueous solution from which the humulate salt was precipitated.3. The method of claim 2 wherein the said cation is selected fromcalcium and magnesium.
 4. The method of claim 3 wherein the solvent forthe water insoluble humulate is aqueous methanol.
 5. The method of claim4 wherein the precipitant for cation is selected from carbon dioxide andalkali metal carbonates.
 6. The method of preparing anisohumulone-containing hop extract which comprises contacting a solutionof an extract of hops, the solvent of said solution being awater-immiscible solvent which dissolves alkali metal humulate saltsless readily than does water, with a sufficient amount of a diluteaqueous alkali metal carbonate to form a mixture of saidwater-immiscible solvent solution and said dilute aqueous alkali metalcarbonate having a pH sufficient to transfer the humulones into theaqueous phase as humulate salts but not sufficiently high to transferthe lupulones into the aqueous phase as lupulate sAlts, forming awater-immiscible phase containing the lupulate salts and a diluteaqueous phase containing the humulate salts, separating said diluteaqueous phase from said water-immiscible solvent, said water-immisciblesolvent being sufficiently polar to extract the humulate salts from saiddilute aqueous phase, recovering said humulate salts from saidwater-immiscible solvent, forming a concentrated aqueous solution ofsaid humulate salts and isomerizing said humulate salts by heating saidconcentrated aqueous solution.
 7. The method of claim 6 wherein thewater immiscible polar solvent is selected from low boiling esters,ketones and water-immiscible alcohols.
 8. Method according to claim 6wherein a water soluble salt having the same alkali metal cation as thehumulate is added to the aqueous phase prior to the separation thereoffrom the water immiscible phase.
 9. Method according to claim 8 whereinthe water immiscible polar solvent is contacted with excess aqueousmineral acid after separation from the aqueous alkali phase.
 10. Methodaccording to claim 9 wherein the acidified solution is contacted withpotassium hydroxide.
 11. Method according to claim 10 wherein potassiumhumulates are recovered from the acidified solution by evaporation ofthe water immiscible polar solvent and isomerized by contacting with ahot aqueous potassium alkali.